The long term goal for this project is to synthesize modified nucleotide which can be incorporated into triplex forming oligonucleotides (TFOs) to enhance the stability of triplex DNA. DNA triplexes are formed when TFOs binding with their corresponding DNA duplex targets. One way to enhance triplex stability may be through electrostatic attraction between the negatively charged phosphate backbone and a positively charged base. In an earlier attempt to accomplish this, we investigated the system involving the positively charged nucleoside 3-methyldeoxycytidine. Although all of the experiments on this compound have not yet been completed, preliminary results indicate that enhancement in stabilization by this compound may be not very high. A potentially better candidate for determining enhancement of stabilization by a positive charge may be achieved by investigating the system involving 7-methyl2- deoxyguanosine (7-MedG) and 7-deaza-7-methyl-2--deoxyguanosine (7c- MedG). In both these nucleosides, all of the Watson-Crick hydrogen bonding groups are still available. In addition, the base in 7-MedG is positively charged whereas it is neutral in bonding groups are still available. In addition, the base in 7-MedG is positively charged whereas it is neutral in 7c-MedG. Thus, triplex binding studies involving TFOs containing these residues with corresponding DNA targets can lead to the direct evaluation of the charge contribution. Moreover, a similar between targets can lead to the direct evaluation of the charge contribution. Moreover, a similar comparison between targets can lead to the direct evaluation of the charge contribution. Moreover, a similar comparison between the control TFO (containing dG) and one containing 7c-MedG would allow for the determination of the contribution of the methyl group to triplex stability. Oligonucleotides containing dG (control), 7-MedG and 7c MedG will be synthesized and their stabilities with respect to duplex and triplex formation will be assessed by uv melting studies. Finally, dinucleotide monophosphates containing these components will be studied by nmr to obtain information related to their conformation in solution.